1. Technical Field
The present invention relates to secondary power systems for aircraft and, in particular, to an integrated air conditioning and power unit for an aircraft.
2. Background Art
In modern high-speed aircraft, weight reduction, space reduction, and cost reduction are highly important. Currently, gas turbine auxiliary power units (APU) are being used to start the thrust engines, and to power the air conditioning and environmental control systems while the aircraft is on the ground. U.S. Pat. No. 4,684,081 issued to Cronin discloses a system which integrates the auxiliary power unit (APU), emergency power unit (EPU), environmental control system (ECS), and engine start system (ESS) in order to reduce the number of parts, weight, and size of the aircraft. The auxiliary power unit is commonly considered to be a low-utilization device that adds weight and complexity to the airplane while providing little operational benefit during most flight conditions. However, the elimination of the APU would require that a substantial pneumatic ground cart and electric ground power cart accompany the aircraft until the main thrust engines are started.
3. Disclosure of Invention
The system of the present invention provides an integrated air conditioning/emergency power system (IAC/EPS) which utilizes electric motor driven vapor cycle refrigeration machinery in combination with an air turbine and compressor to produce an air conditioning/environmental control module which will also serve as a source for emergency electrical power.
The system provides an integrated air conditioning and power unit for use with an aircraft including an air turbine having air passages connected to one of an air inlet and a compressor of a gas turbine engine of the aircraft. A motor/generator is provided drivingly attached to the air turbine and connected to an electric power converter which is connected to a primary power system. The motor/generator is capable of drawing electricity from the primary power system and of generating electricity which is delivered to the primary power system. An air compressor is drivingly connected to the motor/generator. The air compressor includes an air passage connected to one of the air inlet and the compressor of the engine. A cooling system is provided which includes a system compressor drivingly connected to the motor/generator. A first evaporator is connected to the system compressor by a fluid passage, and a condenser is connected between the system compressor and the first evaporator by fluid passages. The air compressor includes an air outlet for providing pressurized air which is cooled by the first evaporator of the cooling system.
The cooling system further includes a second evaporator fluidly connected to the system compressor and a recirculation fan for drawing air from inside the aircraft cabin through the second evaporator.
The integrated air conditioning/emergency power system according to the present invention provides mechanical and electrical equipment in such way that the same equipment or major parts of it can be used to perform a multiplicity of functions. In this manner, a minimum of equipment is installed on the aircraft to perform all the required functions and to provide the required redundancy and reliability.
The integrated air conditioning/emergency power system according to the present invention, in some modes, will take advantage of the pressure energy in the ram compressed air before it goes through the engine compressor. The ram air utilized is at a lower temperature than the compressor air and therefore requires less processing than compressor bleed air.
In some cases, the ram compressed inlet air will have sufficient pressure to drive the vapor cycle unit, or to operate the unit in the emergency electrical power mode.
Some operational modes for the present invention will jointly use ram compressed air with engine compressed bleed air to drive the cabin pressurization and cooling equipment, with no requirement for electrical power input from the aircraft electrical power system.
In an emergency mode, the integrated air conditioning/emergency power system unit will perform as an electrical power generator. This precludes the need to install alternate emergency electrical generating equipment (e.g. ram air turbines/generators). The unit, operating in this mode, may be powered by bleed air from any functioning engine on the aircraft.
During supersonic flight, at which time the ram air is hot, the integrated air conditioning/emergency power system unit will provide cooling and cabin pressurization using bleed air or a combination of electric power and bleed air. The integrated air conditioning/emergency power system can also be used under these conditions to extract pressure and/or thermal energy from the hot bleed air, which can then be either used directly in the cabin or passed through the vapor cycle evaporator for further cooling.
During engine bleed extraction for anti-ice purposes, the proposed arrangement will extract heat and pressure from the bleed air and convert it into usable shaft energy for air conditioning or to produce electrical power. This would reduce the pressure and temperature of the bleed air to parameters usable for anti-ice and may replace the function of, and in some cases, preclude the need for the air pre-cooler and the pressure regulator which is presently used on conventional installations.
The integrated air conditioning/emergency power system arrangement provides a compact means of conveying the heat from the cabin recirculation air to the fuel mass. In this mode, the unit would be driven either by bleed air, the electric motor, or a combination of the two.
With the system of the present invention, any aircraft not having an auxiliary power unit could be operated using only one type of ground support cart and it could be either a pneumatic cart or electrical power cart. Use of either cart would allow engine starting or air conditioning while on the ground.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood however that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.